Frequently asked questions

The science

The long-term solution

Interim beach works at Semaphore and Largs Bay

Semaphore South dune restoration

Securing the future of our coastline

The problem

What is the current state of our metropolitan beaches?

Some parts of the Adelaide beaches are experiencing significant sand loss and erosion of the sand dune system.  The sand along Adelaide’s coast naturally moves northward, by the wind and waves. This causes sand to build up on our northern beaches such as Semaphore, and causes sand loss and erosion along our southern and central coast such as West Beach and Henley Beach South. The State Government manages the metropolitan coastline to enable the community to enjoy sandy beaches. Works to move sand has occurred across the metropolitan beach system for more than 40 years.

  • West Beach has had serious and ongoing erosion for a number of years.  At present, beach levels at West Beach and Henley Beach South are lower than at any other time since records began. 
  • From Henley Beach to the north, the beaches are generally in good condition as the sand lost from southern beaches drifts north. 
  • Sand continues to accumulate in Largs Bay, with wide dunes from around the Semaphore jetty northwards.
  • The beaches in the southern part of the coast (from Glenelg to Kingston Park) are generally stable because of successful beach management. The pipeline from Glenelg to Kingston Park currently pumps approximately 100,000 cubic metres (m3) of sand successfully each year.

Read an article from InDaily ‘Shifting sands – why SA pays for an endless cycle of beach replenishment

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What has been the impact of our eroded beaches?

The erosion at West Beach has had a number of impacts.  Immediately north of the boat harbour the dunes have receded many metres, relying on regular recycling of sand from further north to manage the erosion. 

Further north, the beach at the West Beach Surf Life Saving club has been mostly eroded and the clubhouse, coast park and car park rely on a seawall for protection. 

At the northern end of the seawall, the erosion has lowered the beach so that the beach access ramp is sometimes closed.  The loss of dunes in this area has placed assets at risk, and is requiring regular replenishment to maintain protection levels.

The erosion has progressed to affect Henley Beach South, with much of the sand dunes in front of the seawall being affected.  

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The science

What is the DHI report? What does it say?

In 2017, a coastal processes modelling study was commissioned by the Department for Environment and Water, the Coast Protection Board, the City of Charles Sturt and West Beach Parks to better understand the coastal processes at West Beach and to examine alternative management options. This was needed because of the ongoing loss of sand each year at West Beach. 

External consultants DHI completed a report in 2018. 

  • The research undertaken by DHI has shown that the sand loss at West Beach (the section of coastline running north from the West Beach boat harbor at West Beach Parks to the Torrens Outlet) is significant, and greater than previously estimated. 
  • The report made it clear that even if current management activities were maintained, erosion will continue around West Beach and Henley Beach South, and progressively move north.
  • The report tested out three alternative scenarios for managing the beach and dune erosion at West Beach, with their results modelled. All three options involve beach replenishment, and varied by bringing in differing amounts of sand over different timescales. 

Feedback from local government, industry and community stakeholders, together with the best available research and modelling has been taken into consideration in final decision making. (See What is the government doing to address the problems in the long term?)

 

During the course of the study, the scope was amended to expand the analysis of beach profiles along the entire system from Kingston Park to Largs Bay, to enable a better understanding of the influence of management of adjacent beaches on West Beach and vice versa.  This expanded analysis also provides insight into the management of the entire Adelaide beach system.

The long-term solution

What is the government doing to address the problems in the long term?

In June 2019, the government announced a $48.4 million investment to the metropolitan coast over four years. This consists of $20 million for additional sand including approximately 500,000 cubic metres (m³) of newly sourced sand; and $28.4 million for the completion of a sand recycling pipeline from Semaphore to West Beach, as well as sand dune restoration and revegetation in partnership with local councils and coastal community groups.

The beach replenishment will put sand on our most vulnerable and eroded beaches including West Beach and Henley Beach South, with benefits to other beaches as sand naturally moves northward.

The announcement has been informed by research completed in 2018 by external consultants DHI on behalf of the Department for Environment and Water, the Coast Protection Board, the City of Charles Sturt and West Beach Parks.

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When will it start?

In 2019/20 and 2020/21, we’ll be increasing our beach replenishment to West Beach and Henley Beach South each year to match current rates of loss and stabilise and maintain the beaches and dunes in the short term. (See: Interim beach works at Semaphore and Largs Bay)

Then in 2021/22, a large scale replenishment using sand from an external source (outside of the Adelaide beach system) is planned to be delivered. This will raise the beach levels and boost sand dune buffers at West Beach and Henley Beach South with benefits to other beaches as sand moves northward. (See: Where will the sand come from and why do we need an 'external' sand source?)

Following the project planning phase (including detailed designs, engineering, community consultation and approvals), the pipeline is planned for construction in 2021/22, with the pipeline operational by end 2022/23.

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Where will the sand come from and why do we need an ‘external’ sand source?

There is a finite amount of sand in Adelaide’s beach system. To find a suitable external sand source for the large scale beach replenishment, we are investigating offshore sand deposits as well as land-based sources (quarries). The Securing the Future of Our Coast project is looking to source 500,000m3 of external sand to replenish West Beach. (See: What is being done to source sand from outside of the Adelaide beach system?)

Sand will also continue to be moved to West Beach from Adelaide’s northern beaches in 2019/20 and 2020/21. This is being done to restore sand that is currently being lost from West Beach and Henley Beach South each year while external sand is sourced and the sand recycling pipeline is constructed. (See: Interim beach works at Semaphore and Largs Bay)

Watch the video to learn more about how we manage Adelaide’s beaches

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The Semaphore South breakwater (pictured at the far end of the beach in photo)
is the primary source of sand to replenish Adelaide’s eroding southern beaches. 


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Sand is also being moved from the beach between the Semaphore and Largs Bay jetties.
This photo was taken two weeks after sand was collected in November 2019. 

How will this impact our northern beaches, like Semaphore?

Management of the entire metropolitan coast needs to be adaptive and flexible. Our beaches are constantly changing and sand is naturally moved northward by the wind and waves, which causes sand to build up on our northern beaches, such as Semaphore, but causes erosion along our southern and central coast such as Seacliff, Brighton and Henley Beach.

A sustainable approach to managing our beaches involves recycling sand from areas of where sand builds up to areas of loss. Investigations have taken place to see if sand in other northern beaches is suitable to use for beach replenishment while the pipeline is built and before sand from an external source is available. 

Sand is being collected periodically from beaches between the Semaphore jetty and Largs Bay jetty, which have large sand accumulations, to supplement the amount of sand collected from the Semaphore South breakwater. (See ‘Why is sand being collected between the Semaphore and Largs Bay jetties?’)

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Why are we building a sand recycling pipeline and where will it be located?

A sand recycling pipeline from Semaphore to West Beach will provide an efficient means to recycle sand. This will provide a long term solution to keeping sand on our most exposed and vulnerable beaches.

Pipelines provide more flexibility in managing our beaches – with multiple intake and discharge locations allowing sand to be picked up where there is an accumulation and delivered to locations most at need across the beach system. We have seen this success with the Glenelg to Kingston Park pipeline, which currently pumps approximately 100,000m3 of sand each year.

Another major benefit of the pipeline is reducing the reliance on trucks to move sand, making it safer for the community, as well as reducing noise, congestion and the impact of trucks on roads.

The exact location of the pipeline and how it will be built will be determined in the planning and design period starting in 2019-20.

You can find out more about the existing sand recycling pipeline and how it works, including technical information here.

What impacts will building the pipeline have on our beaches and dunes?

We will minimise the impacts as much as possible during construction. The community will be kept informed and have opportunities to find out more in the coming months.

There will be short-term impacts from construction.  Disturbance of existing dunes and ecological communities will be avoided or minimised.

The works will recycle sand each year to maintain critical dune buffers. This provides the base for dune restoration for the foreshore at West Beach and Henley Beach South in particular. The government will partner with the community and councils to revegetate the foreshore and develop stable sand dunes with vibrant ecological communities.

Community engagement

There will be some impact for residents and beach goers as these works are undertaken. We want to ensure that those who enjoy coastal activities and who live and work along Adelaide’s metropolitan coast are kept informed during all phases of the Securing the future of our coastline project.

We are working closely with local councils, businesses, clubs, non-government organisations and community groups to keep them updated with interim beach management works and will continue to do so.

View the Securing the future of our coastline timeline.

Community Reference Group

A Community Reference Group is being established to help guide the Securing the future of our coastline project. An initial series of online meetings were held in April 2020 with representatives from councils and the community (View the meeting notes). This was the beginning of an information exchange process to enable community to present their initial views and questions. The department will continue to engage with these groups to support this process.

In the initial series of information sessions with community representatives, the importance of undertaking an independent assessment on the northern beaches emerged as a strong theme. The department has agreed to commission an independent review to assess the impacts of moving sand from the northern beaches. This review will include assessing the shorter term impacts of the interim sand movement works (see: Interim beach works at Semaphore and Largs Bay) and the longer term impacts of the sand recycling pipeline implementation. A working group including community representatives will be involved in the process. 

How will the community be kept informed?

The Community Reference Group will provide important input as we plan for and consider the physical, engineering and environment impacts leading up to the construction of the sand recycling pipeline in 2023. The group will provide valuable links to the wider community.

The broader community will be kept informed about the project, including through public events and information sessions.

Sign up to be kept informed.

Events

Sand recycling pipeline tours

We are taking expression of interests for those who wish to join a community tour to see firsthand the Glenelg to Kingston Park pipeline in action. This tour is highly recommended if you wish to learn more about how Adelaide’s metropolitan beaches are managed and the operations of a sand recycling pipeline. Experts will be on hand to answer your questions. The tours are planned for later in 2020 and you will be notified the date/s when confirmed.  If you are under 18 you will be required to have a parent / guardian with you at all times.

Coast Info Van

Keep a look out for the coast info van in your area, where you can learn more about the project and how we manage Adelaide’s beaches. Our team are there to listen and help with any questions you may have about beach works or the broader Securing the future of our coastline project.  

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Due to current restrictions the info van is currently unattended.  

Community group presentation

If you belong to a community group, progress association, or a club, you can book a 30 minute group presentation and Q&A with the project team.

All events must be in line with current COVID-19 restrictions.

For all events enquiries, registrations and bookings please contact DEWCoasts@sa.gov.au or phone (08) 8124 4928.

Staying informed

  • The Coast eNews is a great way to stay informed on interim beach management works and other coastal projects. Sign up to receive updates and encourage others to subscribe as well.
  • Be proactive and keep your networks informed. Ask us to provide your group with content and photos or other graphics suitable to update your community Facebook page.
  • Follow Environment SA News on Facebook and Twitter for further updates.

How else can I get involved?

The department is committed to working in partnership with local councils and coastal community groups on sand dune restoration and revegetation in stage 2 of the project 20/21. Further announcements will be made via this website and the Coast e-news, so make sure you subscribe. 

Available resources

Securing the future of our coastline information booklet is coming soon and will be available for download and distribution.  You will have the opportunity to request printed copies for public display and distribution within your communities.  

Aboriginal Engagement

The project team has commenced engagement with Kaurna via the Department for Environment and Waters First Nations Partnership and Reconciliation Unit to discuss broader engagement and project involvement opportunities.  

What engagement with local businesses has there been?

The government liaise with local businesses who may be impacted by beach works. We work to minimise disturbance to the community as much as possible by not operating during school holidays or on weekends.

Don’t we already have a pipeline?

Adelaide’s two existing underground sand recycling pipelines - Glenelg to Kingston Park and Torrens Outlet to the West Beach dunes - were completed in 2013 to transfer a slurry of sand and seawater from beaches where sand is building up, to the eroding beaches further south.

The pipeline from Glenelg to Kingston Park currently pumps approximately 100,000m3 of sand successfully each year.

This project will extend the pipeline from the northern beaches, to connect to the existing infrastructure at Torrens Outlet to the West Beach dunes.

What happened to the sand moved to West Beach over the last year?

The West Beach area has been eroding since the 1960s and has received many hundreds of thousands of cubic metres of sand to manage the area over the years. Previously it was estimated that sand depleted from the West Beach area was about 50,000 m³/year. Most of this is through natural northward movement, with very little lost offshore.

The new research undertaken by DHI estimates that annual depletion is actually between two and three times that rate, meaning that even when current replenishment activities are taken into account there is a net annual loss of approximately 60,000 m³.

Windy weather and strong waves have caused erosion to continue at West Beach, and when beaches are replenished with sand it is normal for some of it to be washed away during the next storm. If the replenishment sand wasn’t there, then West Beach would be even more eroded and exposed.

Much of the sand that is washed offshore during storms is moved back onshore during calmer periods, so it is not wasted.  This sand will also help maintain beaches as it drifts naturally to the north.

Adding sand to the Adelaide beach system benefits more than just West Beach, it also ensures there is more sand to flow between the beaches and be recycled.

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Why aren't structures like groynes built to try to reduce the natural drift of sand northward? 

Structures of the size required to have an impact are very expensive to construct. These areas would then require large volumes of sand to be brought in from an external source to “pre-fill” them. This pre-filling with external sand is essential otherwise the coast to the north of each structure would be eroded.

In addition, the experience with structures on the Adelaide coast and elsewhere in South Australia is they also trap large quantities of beach-cast seagrass, which has an impact on the usability of the beaches and increases management costs.

When factoring in these aspects, the sustainable approach to managing our beaches involves recycling sand from areas where sand builds up to areas of loss. This means the protection of Adelaide’s beaches can be achieved without negative impacts from structures, which would tend to interrupt our long sandy beaches.

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By building a structure or structures like groynes and breakwaters that slow sand movement along the coast, the area in the vicinity of the trapped sand can be protected.  However, the coast to the north (down-drift) of the structure will then be starved of sand unless the area is replenished.

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An example of the use of structures along the beach in Japan.

Options involving the construction of hard engineering structures to re-orientate the West Beach shoreline were considered by DHI and included offshore breakwaters and headland control structures. A range of risks and disadvantages were identified with these options. The DHI report does not model any management options that use structures to retain sand on the beaches. 

Why does Seacliff beach look so good? How has dune restoration helped?

During the 1980s and 1990s, the Seacliff and Brighton coast was suffering from severe erosion that threatened the foreshore. To address this, a large scale beach replenishment with sand sourced externally was undertaken.

During the 1990s over 1 million cubic metres of sand was dredged from sand deposits offshore of Port Stanvac and delivered to that section of the coast, which formed and stabilised the dunes and in turn helped to stabilise the beach.

The operation of the sand recycling pipeline from 2013 onwards has maintained sand volumes and further stabilised this part of the coast and will continue to do so as required.

Seacliff Beach 1981Seacliff beach 2012

What is being done to source sand from outside of the Adelaide beach system?

Preliminary investigations are being undertaken to find a suitable sand source from outside of Adelaide’s beach system (external sand) for a large scale beach replenishment needed for West Beach.

We are investigating offshore sand deposits as well as land-based sources (quarries). The Securing the Future of Our Coast project is looking to source 500,000m3 of external sand to replenish West Beach. (See: What is the government doing to address the problems in the long term?)

No decision has yet been made on where the sand will come from.

Preliminary investigations will map habitat zones and determine the nature and extent of offshore sand deposits. This is just the first step in the process of determining whether there is sand available that would be an economically and environmentally sustainable option for the replenishment of Adelaide’s metropolitan beaches. 

These investigations and other planning and approvals are required before the external sand is delivered. 

Why is sand from elsewhere needed?

Sand from outside of Adelaide’s metropolitan beach system – or ‘external sand’ is needed because there is a limited amount of sand in Adelaide’s beach system.  This is because sand has been ‘locked up’ by building on top of the natural dune systems.

The last large importation of sand into Adelaide’s beach system was in the 1990s when approximately 1.2 million cubic metres of sand from Port Stanvac was supplied to Brighton beach (See: Why does Seacliff beach look so good?). Research undertaken by external consultants DHI considered that this helped sustain Adelaide’s beaches for at least 10 years.

Adding sand to Adelaide’s beach system is needed to raise the beach levels and boost sand dune buffers at West Beach and Henley Beach South. It will also help to address the impacts of rising sea levels.

Can any type of sand go onto the beach?

No, the sand we are looking for both from quarries and from offshore sources needs to have certain characteristics to do the job of beach and dune stabilisation. Coarser sands (larger grain sizes) are better because they are heavier and are less likely to be moved along the coast by wind and waves.

The sand also needs to have a low percentage of silt and clay particles so that plumes aren’t caused after the sand is placed on the beach.

We will collect samples from different quarries, and from offshore deposits, and test them in a laboratory to find the most suitable sand for West Beach.

These investigations and other planning and approvals are required before the external sand is delivered.

When is the sand planned to be delivered to West Beach?

The large scale replenishment using sand from an external source is planned to be delivered in 2021/22. View the project timeline here.

What is being done to help beaches outside of Adelaide?

Local councils play a critical role in protecting regional assets from coastal hazards and maintaining coastal areas for all South Australians and tourists.  The state government has committed an additional $4 million over 4 years to regional coasts to repair, restore and sustain them in partnership with local councils.  This support responds to the increasing demand for coastal protection infrastructure to address hazards like flooding and erosion. 

The program is open to councils with a particular focus on the outer metro and regional areas. Learn more.

Interim beach works at Semaphore and Largs Bay

Sand is being moved from between the Semaphore and Largs Bay jetties to replenish West Beach periodically 2-3 times per year (autumn and spring) in 2020 and 2021.

Read the latest works update

The department is regularly meeting with community representatives and council to help guide the Semaphore sand movement works.

Why is sand being collected between the Semaphore and Largs Bay jetties?

The state government’s long term strategy to manage the erosion at West Beach and Henley Beach South includes a commitment to match the rate of sand loss at these beaches by moving sand in the short term while new sand is sourced from outside of the Adelaide beach system and a sand recycling pipeline from Semaphore to West Beach is built.  (See ‘When will it start? When will the pipeline be built?’).

Due to the natural northward movement, sand builds up at Semaphore. Much is captured at the Semaphore South breakwater. Sand has also accumulated at beaches between the Semaphore and Largs Bay jetties. Sand now needs to be collected from the beach between the Semaphore jetty and Largs Bay jetty to supplement the amount of sand collected from the Semaphore South breakwater

The sand moved from north of the Largs Bay jetty (in April/May 2020) is to restore the eroded dunes at Semaphore South. (See: Semaphore South dune restoration)

Technical and environmental information

What about sand from the beaches further north, like North Haven?

Historically, testing of sand at the northern end of Largs Bay has shown that it would be uneconomic to use it to replenish beaches further south on the Adelaide coast. This is because it is finer and would wash away much more quickly.  The most recent analysis shows that while suitable sand can be found to just north of Largs Bay jetty, the build-up of sand beyond that would not be an economically viable source for replenishing West Beach or its adjacent beaches.

Sand from immediately north of the Largs Bay jetty (to Strathfield Terrace, Largs North) has been used to restore eroded dunes at Semaphore South. (See ‘Semaphore South dune restoration’)

The properties of Adelaide’s natural beach sand has been thoroughly investigated to inform beach management decisions and help identify suitable sources of sand for beach replenishment. 

What will the likely impacts to the dunes between Semaphore and Largs Bay jetties be?

The dunes in between the Semaphore and Largs Bay jetties vary from 80 metres wide to over 100 metres wide, and sand will be sourced from the beach where the dunes are wider.  

Any indication of foredune erosion at this location would be closely monitored to ensure the foreshore remains protected and the wider dune system maintained.

It is expected that this impact will be short-term until Semaphore beach naturally replenishes with sand that naturally moves north again, enabling the foredune to rebuild.

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Semaphore beach two weeks after the sand was collected in November 2019.

How will the impacts to the dunes be managed?

We acknowledge the great work that dune care groups do to look after our beaches and their extensive local knowledge of the dunes. We will work with them to minimise the impacts to our beaches and dunes during this time. There will be opportunities in the future for community groups to partner with the local council for dune care grants to further improve the coastal biodiversity.

We will continue to monitor the beaches and dunes to ensure the foreshore remains protected.

Has an assessment of the dune vegetation been done? 

In March 2020, the department engaged independent ecologists to undertake a vegetation survey to assess and map the flora along 5km length of coast between Semaphore Surf Life Saving Club and Strathfield Terrace, Largs North. The field assessment includes gathering information about native species present, weed species present and their cover category, native plant life forms, native/exotic understorey biomass and tree health.This information will be used to help inform future works including dune restoration at Semaphore South.

What is being done to manage the erosion to the north of the Semaphore South breakwater?

What about impacts to the dunes to the south of the breakwater?

Since October 2018 approximately 178,000 cubic metres of sand has been moved from the Semaphore South breakwater to West Beach and Henley Beach South.

Supplementing this, approximately 20,000 cubic metres of sand has been moved from the beach between Semaphore jetty and Largs Bay jetty to West Beach in financial year 2019-20.

The dunes at Semaphore Park have built up since the Semaphore South breakwater was built in 2005. Some erosion of dunes may result from sand sourcing. There will remain more than enough sand in these dunes to continue to protect the foreshore and development at Semaphore Park.

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The dunes at Semaphore Park were an erosion ‘hot spot’ in the 1980s and 90s and required regular beach replenishment. The dunes have built up since the Semaphore South breakwater was built in 2005. Download poster

Have environmental impacts been considered?

Semaphore has been used as a sand source area at various times since the 1970s and has naturally replenished without causing significant environmental impacts. 

The approach for managing Adelaide’s beaches is based on expert advice underpinned by decades of data collected, including current and historical survey information on beach profiles and independent technical reports. 

At the location between the Semaphore and Largs Bay jetties, the government’s beach profile data indicates that there is sufficient dune volume buffer and the area will steadily build up again through natural processes. A team of environmental specialists monitor and assess Adelaide’s beaches regularly. 

The Department for Environment and Water works with Birdlife Australia to ensure any impacts to shorebirds are avoided or minimised.

The Securing the future of our coast project will improve dune biodiversity in the longer-term along Adelaide’s coast by stabilising the beaches and dunes with a steady supply of replenishment sand and through partnerships with council and community groups. 

See also:

Once the pipeline is built, how much sand will be sourced from Semaphore?

Once operational, the sand recycling pipeline will be used to source sand from areas where sand is built up to replenish areas that are eroding further south.  Analysis of the beach profiles conducted by the Department for Environment and Water will provide information on where sand is accreting or eroding and inform these decisions.  The Semaphore South breakwater, designed to trap sand for replenishment, will continue to be a primary source of sand. 

Average natural sand movement northwards along the coast is approximately 100,000 cubic metres each year, and this will need to be matched by replenishment of West Beach at the southern end of the pipeline pumping system.  The volumes of sand eroding and building up along the beach system will vary from year to year, depending on the shape and height of the sea bed, the weather and storms and this will influence the amount of sand which needs to be collected for replenishment.

Why isn’t dredging or a barge used to move sand instead?

Shifting sand by dredging it onto a barge would be severely limited by weather conditions, increasing the cost and increasing the time taken to conduct beach works. The amount of sand needed to match the rate of loss from West Beach and Henley Beach South could not be moved efficiently and cost-effectively with a dredge. 

Why can’t external sand be brought in now?

There is a limited amount of sand in Adelaide’s beach system and to find a suitable external sand source for the large scale beach replenishment will take time. We investigating offshore sand deposits as well as land-based sources (quarries). (See: External sand investigations).

These investigations and other planning and approvals are required before the external sand is delivered. The large scale replenishment using sand from an external source is planned to be delivered in 2021/22. View the project timeline here.

Why aren’t structures like groynes built to try to reduce the natural drift of sand northward?

Has the department looked at the work done to manage beaches in other areas?

Beach management strategies vary across Australia and internationally due to differences in coastal processes, climate and landscape.  The approach for managing Adelaide’ beaches is based on expert advice underpinned by decades of data collected, review and assessment of methods used around the world, consideration of the issues specific to Adelaide’s beaches, and including current and historical survey information on beach profiles and independent technical reports.

 

Semaphore South dune restoration

Read the project update brochure

What is being done to manage the erosion to the north of the Semaphore South breakwater?

The area immediately north of the Semaphore South breakwater (from approximately Noonies Cafe to Hart Street) is prone to erosion. Sand from near the Semaphore jetty has periodically been used to replenish the eroded section of dunes.

A severe storm in May 2016 caused widespread coastal erosion throughout South Australia. At Semaphore South, much of the dune and its vegetation was lost.

Major replenishment works to restore the dunes and protect the area from further damage by storms commenced in late April 2020. The project aims to rebuild the eroded dunes and stabilise them with vegetation and drift net fencing

The project is being led by the Department for Environment and Water in partnership with the City of Port Adelaide Enfield. The department has been working closely with the City of Port Adelaide Enfield and community representatives to help guide this project. As part of the restoration works the City of Port Adelaide Enfield is installing a new fence and reinstating the turf and irrigation to its former state. 

Semaphore South dune erosion
A section of eroded beach at Semaphore South. Photo taken in April 2020

What is being done to restore the dunes?

Sand has been moved from north of the Largs Bay jetty, where there is a large accumulation, to rebuild the eroded dunes at Semaphore South between Arthur Street and Hart Street. The dunes will be stabilised with vegetation and drift net fencing. Sprinkler irrigation will help the plants establish and grow, and it will also help to reduce wind-blown sand.

When will it be finished?

Dune restoration works commenced in late April and will be completed by the end of July 2020.

  • Sand has been moved from the beach between the Largs Bay jetty and Strathfield Tce, Largs North, to rebuild the sand dunes at Semaphore South. (Stage 1 – completed end May 2020)
  • Drift net fencing, revegetation and sprinkler irrigation will help stabilise the dunes. (Stage 2 – in progress June/July 2020)
  • The City of Port Adelaide Enfield has replaced the boundary fence and is upgrading the turf and irrigation in the area. 

This timing has ensured that a buffer is in place to protect the area for winter when storms causing further erosion are more likely. 

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How is the sand being stabilised?

The sand has been shaped to match the normal dune profile along Adelaide’s metropolitan coast (i.e. a raised fore dune area and lower rear dune / swale behind).

Stabilisation will follow well established methods using drift net fencing and revegetation (refer for example to the Tasmanian Coastal Works Manual for further information).

  • Standard drift net fences, as used extensively in other council areas, is being erected along the dune, parallel to the beach. The drift fences help to trap windblown sand coming from the beach and dune face and provide a more stable environment for establishment of vegetation. 
  • During Stage 1 of the project (moving sand to rebuild the dune) beach-cast seagrass wrack, left on the beach by tides and waves in the vicinity of the works,  was incorporated into the replenished dune at Semaphore South. The seagrass wrack will provide some organic nutrients, assisting plant growth and it will also help to bind the sand
  • Extensive revegetation will follow, in accord with a species list and planting plan provided by independent ecologists who have recently completed a comprehensive vegetation survey of the Largs Bay coast.
  • Ongoing weed control and further planting will occur in subsequent years to increase the biodiversity and resilience of this area. 

These techniques have been used with great success to re-establish dunes on Adelaide’s southern beaches, such as at Seacliff and South Brighton (example pictured below).

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Dune restoration examples at Shoreham Road, South Brighton taken in 1985 and 2018. Photos courtesy City of Holdfast Bay.

Can I access the beach during the works?

The beach remains open during works.

The community and beach users are asked to:

  • Take extra care on the beaches, streets and surrounding area during works.
  • Adhere to safety signs and directions. 
  • Stay off the newly established dunes. This is important so that the sand remains stable and there is no damage to plants. 

Why have some of the beach access tracks been raised in height?

Some of the beach access tracks at Semaphore South have been raised with sand to match the shape of the newly placed dunes. This has been done to ensure that all of this stretch of foreshore is protected from flooding and erosion. This is especially important for the winter months ahead.  The department and council will monitor the area and assess this trial replenishment over the coming months.

The beach access path nearest to Noonies Café has not been raised in height with imported sand. Council will determine if this is suitable temporarily, over the winter months, for the blue accessible mat to be rolled out. 

We apologise for any inconvenience caused during these essential works to protect the foreshore and community assets before winter when storms are more likely. 

Community safety

Community safety is a priority. Safety signage is in place on the beaches during works. 

The community and beach users are asked to please take extra care on the beaches while the works are underway and adhere to all safety signage and flagging in place during operations. Qualified contractors are employed for the works. The successful contractor is required to develop a job safety plan and a thorough risk management plan. This includes safe management between the work and members of the public.  

Traffic control complies with relevant Australian Standards and Code of Practice. Traffic controllers and/or signage is provided where necessary.

We also liaise with Surf Life Saving SA and the Semaphore Life Saving Club regarding beach safety.

Truck speed limits on beaches

Sand movement works on the beaches are undertaken by a contractor on behalf of the department. Safety is of paramount importance when undertaking works along our beaches. As such, the contract includes stringent conditions regarding the speeds that the equipment (trucks and other machinery) can operate at when moving along the beach.

Speed of vehicles on the beach shall not be greater than:

  • 40 km/h unless within 50 metres of any person or animals
  • 25 km/h between 10 metres and 50 metres of any person or animals
  • Must stop within 10 metres of any person or animal
  • 5 km/h within 20 metres of Semaphore Jetty

In addition, all vehicles must give way to all other traffic on the beach including all pedestrian and animal traffic. They must stop when pedestrians or animals wish to cross the line of movement of the trucks along the beach.

GPS monitoring is used to make sure the contractor’s trucks are not speeding. The department also has a full time supervisor on site at the beach monitoring compliance with these conditions. 

How do you know that the sand to the north of the Largs Bay jetty is suitable? 

Historically, sand at the northern end of Largs Bay has proven to be unsuitable for replenishing beaches further south on the Adelaide coast as it is finer and would wash away more quickly. The most recent sand sampling analysis (2019) indicated that sand in the area immediately north of Largs Bay jetty has become coarser over time and is now suitable for replenishing the dunes at Semaphore South.

Large volumes of coarse sand from external sources were added to the southern beaches in the 1990s. It is possible that this sand has now moved northwards into this section of the coast. While suitable for replenishing Semaphore South, the testing showed that sand north of Largs Bay remains unsuitable for replenishing beaches further to the south, such as West Beach.

Largs Bay dunes
Largs Bay beach and dunes, April 2020

 

How much sand has been moved from Largs Bay to Semaphore South?

An estimated 34,000 cubic metres (m³) of sand has been moved to Semaphore South to rebuild the Semaphore South dunes.  This includes approximately 30,000 m3 from the beach north of the Largs Bay jetty to Strathfield Tce, Largs North and approximately 4,000 m3 moved from around the Largs Bay jetty. The new sand dunes have been built to resemble the wider dunes to the north of Hart Street in size and width.

See: Why was sand removed around the Largs Bay jetty?

Why is sand under the surface of the beach grey or black in colour?

The sand collected from Semaphore and Largs Bay is coloured grey to black because of the naturally decomposing seagrass content. This is particularly noticeable if you dig below the surface of the beach in areas where seagrass wrack accumulates. This quickly dries and turns white/yellow after being exposed to the sun, wind and rain.

Could seaweed bales be used to help stabilise the newly placed sand?

Not as part of the trial. Baling seagrass is labour-intensive and beach cast seagrass wrack plays an important ecological function in the coastal environment.

During Stage 1 of the project (moving sand to rebuild the dune) beach-cast seagrass wrack left on the beach by tides and waves in the vicinity of the works was incorporated into the replenished dune at Semaphore South. The seagrass wrack will provide some organic nutrients, assisting plant growth and it will also help to bind the sand.

Is this a one-off project or will it be a regular occurrence?

The project to re-establish the Semaphore South dunes using sand from north of the Largs Bay jetty is a one-off trial project. However, as has occurred in the past, the seaward part of the Semaphore South dunes will erode from time to time and will require periodic replenishment with smaller amounts of sand to maintain the foredune area that is directly exposed to coastal processes. The sand used to replenish Semaphore South in the past has been moved back from the area around Semaphore jetty.

Testing during 2019 showed that sand to the north of Largs Bay jetty is suitable for replenishing the Semaphore South area. Further analysis during the trial would confirm whether this area is another possible location from which sand can periodically be moved back to replenish and maintain the Semaphore South dunes.

What impact will this have to the dunes north of the Largs Bay jetty?

The approach for managing Adelaide’s beaches is based on expert advice underpinned by decades of collected data, including current and historical survey information on beach profiles and independent technical reports. A team of environmental specialists monitor and assess Adelaide’s beaches regularly. Annual beach surveys are undertaken along the coast to measure the beach profiles and assess if there is a sufficient dune volume buffer in the area.

The government has assessed that any environmental impacts on the coastline north of Largs Bay jetty as a result of the proposed removal of the volume of sand required to rebuild the Semaphore South dunes would be minor. The stabilisation and revegetation of the Semaphore South dunes will create significant environmental benefits associated with improved biodiversity outcomes. 

At the location north of the Largs Bay jetty, the government’s beach profile data indicates that there is sufficient dune volume buffer to allow removal of the sand required to rebuild the Semaphore South dunes. Based on previous experience and monitoring of areas where sand has been collected, the impact on the dunes of removing sand from the intertidal zone as part of the trial is expected to be minimal. The area will steadily build up again through natural processes.

The department engaged independent ecologists to undertake a vegetation survey in March 2020 to assess and map the flora communities along the 5km length of coast between Semaphore Surf Life Saving Club and Strathfield Terrace. See ‘Has an assessment of the dune vegetation been done?’

This baseline information has informed species selection for the planting of the restored Semaphore South dunes, will enable any impacts of the trial to be monitored, and will inform future works.

The field assessment includes gathering information about native species present, weed species present and their cover category, native plant life forms, native/exotic understory biomass, tree health, etc. Incidental fauna observations were also recorded.

Largs Bay Jetty looking north
Largs Bay jetty and beach looking north, April 2020

Is there a long-term solution planned for the Semaphore South erosion problem?

The project to rebuild and stabilise the Semaphore South dunes using sand from north of the Largs Bay jetty will not negate the need for ongoing periodic replenishment of the Semaphore South area.

The foredune area would still be subject to coastal processes, including erosion during storm events, and it is expected that replenishment (on a smaller scale) will continue to be required on a periodic basis to maintain the foredune.

Semaphore South has previously been replenished using sand from the Semaphore jetty area. The trial using sand from north of Largs Bay jetty will inform whether this is an additional option for consideration as part of the long term management of the Semaphore South coastline.

Why was sand removed around the Largs Bay jetty?

In May 2020 the department undertook routine maintenance work to remove sand around the Largs Bay jetty on behalf of the Department of Planning, Transport and Infrastructure (DPTI). This is necessary maintenance work in order for DPTI to assess the condition of the jetty and undertake any repairs that may be needed to keep the jetty in good condition. 

The works were undertaken at this time to achieve cost benefits given the contractors were present on site to undertake the works for Semaphore South.

Why is water pooling around the Largs Bay jetty at times?

The nature of the excavation around the jetty, carried out to protect the jetty, means that water may be present from time to time.  This is largely dictated by the adjacent seawater level, and any recent rain. When the tide is very high, water may pool from either rain, or as it rises up from the underlying sea water table. When the tide lowers water is free to drain away. There is also a possibility that storm surges could flow over the low dune at the seaward end of the jetty and deposit seagrass into the lower area behind. This has happened at Semaphore jetty for similar operations.

The department is monitoring the area regularly to assess if pooling water is an ongoing problem.

What community engagement has occurred?

The department has been working closely with the City of Port Adelaide Enfield and community representatives on the project. Community input was sought in March 2020 on the proposal, and the majority of feedback received supported the work to restore the dunes at Semaphore South.

Who can I contact for more information?

For enquiries contact the Department for Environment and Water on 8124 4928 or email DEWCoasts@sa.gov.au

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